55 
Ordinary Meeting, March 5th, 1861. 
Dr. Joule, President, in the Chair. 
Mr. Joseph Sidebotham read a Paper “On the Structure 
of the Luminous Envelope of the Sun,” being a communication 
to him from James Nasmyth, Esq., of Penshurst. 
Mr. Nasmyth has made the discovery, that the entire 
surface of the sun is composed of objects of the shape of a 
willow leaf ; these objects average about 1,000 miles in length, 
and 100 in breadth, and cross each other in all directions, 
forming a network ; the thickness of this does not appear to 
be very great, as through the interstices the dark or penumbral 
stratum is seen, and it is this which gives to the sun that peculiar 
mottled appearance so familiar to observers. These willow 
leaf-shaped objects are best seen at the edges of a solar ‘spot 
w here they appear luminous, on a dark ground, and also com- 
pose the bridges which are formed across a spot ’ when it is 
mending up; the only approach to symmetrical arrangement 
is in the filaments bordering the spot, and those composing 
the penumbra, which appears to be a. true secondary stratum 
of the sun’s luminous atmosphere ; here these bodies show a 
tendency to a radial arrangement. Although carefully 
watched for, no trace of a spiral or vortical arrangement has 
been observed in these filaments; thus setting aside the 
likelihood of any whirlwind-like action being an agent in the 
formation of the spots, as has been conjectured to be the case. 
The writer does not feel warranted at present in hazarding 
any conjectures as to the nature and functions of these 
remarkable willow leaf-shaped objects, but intends pursuing 
the investigation of the subject this summer, and hopes to lay 
the results before the British Association during their meeting 
in this city. The Paper was illustrated by three beautiful 
drawings. No. 1 represented one of the willow leaf-shaped 
objects ; No. 2 the luminous surface of the sun as being entirely 
Proceedings — Lit. & Phil. Societt— No. 11. — Session, 1860-61. 
